1. Field of the Invention
The present invention relates to devulcanized rubber manufactured to recycle a discarded vulcanized rubber, a method of manufacturing the devulcanized rubber, and a method of manufacturing reclaimed molded rubber products from the devulcanized rubber.
2. Description of the Related Arts
The conventional method is carried out as follows to recycle discarded vulcanized rubbers such as used tires, scraps generated in manufacturing molded rubber products, and discarded defective products: Initially, the vulcanized rubber is pulverized into coarse particles, and then devulcanizing treatment is performed; i.e., sulfur crosslinking bonds in the vulcanized rubber are cut to form it into devulcanized rubber. Then, the devulcanized rubber is vulcanized and molded to obtain products having a desired shape.
A devulcanizing method called PAN method is known. In this conventional method, after chemical devulcanizing agent and reclaiming oil are added to the discarded vulcanized rubber, the mixture is treated in an autoclave at 200.degree. C. and a water vapor pressure of 14.5 kg/cm.sup.2.
The devulcanized rubber according to the conventional method is, however, poor in its quality. Reclaimed rubber products manufactured by vulcanizing the devulcanized rubber again and molding it into desired shapes do not have the rubber characteristic suitable for practical use.
In order to solve this problem, as an ordinary method of manufacturing molded rubber products from the devulcanized rubber, 20-30 parts by weight of the devulcanized rubber is added to 100 parts by weight of virgin unvulcanized rubber to form devulcanized rubber material, and then the devulcanized rubber material is vulcanized and molded to obtain reclaimed rubber products having desired shapes.
The molded rubber products processed from the devulcanized rubber thus obtained has the rubber characteristic suitable for practical use. But the conventional method is incapable of recycling a great amount of discarded vulcanized rubber such as automobile tires.
Thus, in the conventional method, virgin rubber must be mixed with devulcanized rubber to obtain reclaimed rubber having rubber characteristic suitable for practical use.